Consolidatable epoxy resin-coated particulate materials have been used heretofore in various well treatment operations. Consolidatable epoxy resin-coated sands have been used, for example, for gravel packing, for the development of controlled permeability synthetic formations within subterranean zones, and as proppant materials in formation fracturing operations. Due to their desirable permeability and compressive strength characteristics, consolidatable epoxy resin-coated particulate materials are especially well-suited for treating semiconsolidated and unconsolidated formations which contain loose or unstable sands.
As used herein, the term "consolidatable epoxy resin-coated particulate material" refers to a particulate material which is coated with an uncured or only partially cured epoxy resin composition. Typically, the consolidatable epoxy resin-coated particulate material will be injected into a subterranean zone using procedures whereby the epoxy resin does not substantially harden until after the particulate material has been delivered to a desired location within the formation. The consolidatable epoxy resin-coated particulate material will typically harden within the formation to form a hard, consolidated, permeable mass.
Well treatment methods utilizing consolidatable epoxy resin-coated particulate materials are disclosed, for example, in U.S. Pat. No. 5,128,390. The entire disclosure of U.S. Pat. No. 5,128,390 is incorporated herein by reference.
U.S. Pat. No. 5,128,390 discloses a method for continuously forming and transporting consolidatable resin-coated particulate materials. In the method of U.S. Pat. No. 5,128,390, a stream of gelled aqueous carrier liquid is continuously mixed with a particulate material (e.g., sand), a hardenable epoxy resin composition, and a surface active agent. The resulting continuous composition is delivered to and/or injected into a desired subterranean zone. As the continuous mixture flows down the well tubing toward the subterranean zone, the composition ingredients are thoroughly mixed such that the gel-suspended particulate material is coated with the hardenable epoxy resin composition. After being placed in the subterranean zone, the epoxy resin composition is allowed to harden whereby the resin-coated particulate material forms a hard, permeable, consolidated mass.
The hardenable epoxy resin composition used in the method of U.S. Pat. No. 5,128,390 is generally composed of: a polyepoxide resin carried in a solvent system; a hardening agent; a coupling agent; and a hardening rate controller. The hardening agent used in the method of U.S. Pat. No. 5,128,390 is either (a) an amine, a polyamine, an amide, and/or a polyamide dissolved in a suitable solvent or (b) a liquid eutectic mixture of amines diluted with methyl alcohol.
Unfortunately, well treatment methods of the type disclosed in U.S. Pat. No. 5,128,390 are not well-suited for use in high temperature subterranean formations. Consolidated epoxy/hardener compositions of the type used in the methods of U.S. Pat. No. 5,128,390 typically cannot withstand temperatures substantially exceeding about 200.degree. F. However, such temperature conditions are commonly encountered in subterranean formations.
Thus, a need presently exists for a consolidatable resin-coated particulate material and method which can be used for treating high temperature subterranean zones and formations (i.e., zones and formations having temperatures exceeding about 200.degree. F.).
Diaminodiphenylsulfone (DDS) has been used heretofore as a hardener in certain epoxy resin compositions. DDS generally provides high temperature resistance and high chemical resistance properties. At ambient conditions, DDS is typically a solid material which will not substantially dissolve in most of the solvents and/or diluents used in epoxy resin systems. Thus, when blending DDS with an epoxy resin, the blend components must typically be heated sufficiently to enable the DDS to be dissolved in the epoxy resin system.
In view of the difficulties encountered when blending DDS with epoxy resins, the use of DDS as an epoxy resin hardener in well treatment operations has not heretofore been a viable alternative. The heating and blending operations required for dissolving DDS in epoxy resin systems typically cannot be economically and conveniently conducted at the well site. Additionally, it is generally not possible to perform the blending operation off-site and then deliver the DDS/epoxy resin blend to the well site since: (a) the resulting DDS/epoxy resin composition will typically have a very short pot life; (b) the DDS/epoxy resin composition will, in many cases, harden before it can be delivered to the well site and used; and (c) even if the blend does not harden before use, any excess material produced and delivered to the well site is simply wasted.